1. Field of the Invention
This invention relates to the use of a plasma or a glow discharge for dissociating one or more gases into reactive and non-reactive ionic and reactive and non-reactive neutral species, and in particular, to de-activating such a plasma.
2. Description of the Prior Art
Plasma apparatus can be divided into two broad categories, downstream or remote plasma and direct plasma. In downstream plasma, the article(s) are not immersed in the glow discharge, as it is in direct plasma. The result is a purely chemical and multi-directional process resulting in a somewhat more gentle treatment of the article(s) because high power electromagnetic waves at high frequency are not coupled through the article(s) and there is no heating from direct ion bombardment. In either type of apparatus, it is known in the art to employ some type of plasma for processing one or more article(s).
Typically, one or more reactive gases (such as, oxygen-based gases, or halogen-based gases, including fluorine, chlorine, bromine, or other equivalent gases, as well as gas molecular compounds having one or more oxygen or halogen atoms), are used in combination with other gases due to the highly reactive nature of the reactive gas(es), in a plasma chamber.
In the prior art, a major problem to solve in order to obtain an electrically charge free process is the need for de-activation of a plasma, such as the need for recombination of the charged particles to form neutral particles. De-activation of the plasma means the removal of all electrically charged reactive and un-reactive species from the plasma. In the prior art, the de-activation of a plasma is achieved by using a long path (up to one meter in length) from the plasma chamber to a sample chamber, or the use of baffles to essentially increase the path length by convolutions so that a plasma is de-activated before it reaches the sample chamber. Another option is to use a wire mesh screen between the plasma generation chamber and the sample chamber to form a Faraday shield.
Another problem in the prior art is that the means used to eliminate the electrical charges also results in a loss of the desired reactive neutrals.
In view of the foregoing, what is needed is an improved method and apparatus for efficiently and selectively de-activating a plasma to eliminate the reactive and non-reactive electrically charged species.